Endogenous intact PTH is suppressed during teriparatide (rhPTH 1-34) administration in postmenopausal women with established osteoporosis

Abstract

Introduction: Teriparatide (recombinant human PTH 1-34/TPTD) is an osteoanabolic agent available for osteoporosis treatment. The aim of this prospective trial was to evaluate the acute and chronic effects of TPTD in endogenous intact PTH (iPTH) levels in postmenopausal women with established osteoporosis. Materials and methods: Thirty-six postmenopausal Caucasian women (age 66.6 +/- 1.4 years) with established osteoporosis received TPTD 20 mu g once daily for eighteen months. Follow-up was continued for another six months after treatment discontinuation for a total of 24 months. Serum calcium, phosphate, total alkaline phosphatase (ALP) and iPTH were obtained from all women before and one hour, one day, as well as one, six, twelve, 18 and 24 months after treatment initiation. Lumbar spine bone mineral density was measured before, as well as twelve and eighteen months after treatment initiation. Results: iPTH levels decreased from the first hour of treatment, remained suppressed as long as TPTD was administered and increased after treatment discontinuation (p < 0.001). Total ALP followed an opposite pattern. Serum calcium remained within normal range. Conclusions: iPTH levels are suppressed rapidly and persistently during TPTD administration whereas they return to baseline after treatment discontinuation; therefore, they can serve as an index of patient's compliance to treatment.